This invention relates to a method of working a hub ring of a wheel bearing assembly and a device therefor.
Among vehicle wheel bearing assemblies, there are ones for driving wheels and ones for non-driving wheels. FIG. 6 shows one example. This wheel bearing assembly is for a driving wheel and comprises an outer member 1, an inner member 2 and double-row rolling elements 3 mounted between outer and inner members 1 and 2.
On the outer periphery of the outer member 1, a vehicle body-mounting flange 4 is formed, and on inner periphery thereof, double-row bearing raceways 5 are formed.
The inner member 2 comprises a hub ring 2a as a first rotary member and a raceway member 2b as a second rotary member. On the outer periphery of the hub ring 2a, a wheel-mounting flange 6 and a bearing raceway 7 opposite one of two bearing raceways 5 formed on the outer member 1 are formed. Hub bolts 8 are provided on the wheel-mounting flange 6. On the outer side of the hub ring 2a, a wheel pilot portion 9a and a brake pilot portion 9b are provided. The latter is located at the root of the wheel-mounting flange 6. On the inner side, a small-diameter portion 10 is provided. The hub ring 2a is formed with a spline through hole 11 extending from the end face of the small-diameter portion 10 to the bottom of the wheel pilot portion 9a. 
On the outer peripheral surface of the small-diameter portion 10 of the hub ring 2a, a fitting surface 10a receiving the raceway member 2b, the raceway 7, and a seal land 10b are formed. On the raceway member 2b, a bearing raceway 12 opposite the other of the double-row bearing raceways 5 formed on the outer member 1 is formed.
The double-row rolling elements 3 are mounted between the double-row bearing raceways 5 provided on the inner periphery of the outer member 1 and the bearing raceway 7 and 12 formed on the hub ring 2a and raceway member 2b, respectively, to support the outer member 1 and the inner member 2 rotatably. Also, seals S are mounted at both ends between opposed surfaces of the outer member 1 and the inner member 2 to prevent entry of dust.
In mounting the wheel bearing assembly to a vehicle, the flange 4 formed on the outer member 1 is secured to the vehicle body by tightening bolts.
Also, wheel nuts 14 are tightened onto the hub bolts 8 provided on the wheel-mounting flange 6 to mount a brake rotor 13 and a disc wheel to the wheel-mounting flange 6.
In such a wheel bearing assembly, since run-out of the braking surface 13a of the brake rotor 13 during rotation causes brake judder during braking, high working accuracy and high dimensional accuracy are required for each part of the wheel bearing assembly.
In particular, since the outer side of the wheel-mounting flange 6 of the hub ring 2a is the mounting surface for the brake rotor 13, the working accuracy of the hub ring 2a influences the run-out of the brake rotor 13.
Heretofore, as shown in FIG. 7, in grinding the hub ring 2a, a backing plate 20 was pressed against the wheel pilot portion 9a, the bearing raceway 7 was supported by a shoe 21 with the end face of the wheel pilot portion 9a as a reference, and the bearing raceway 7, the fitting surface 10a for the raceway member 2b, and the seal land 10b were simultaneously ground by use of a grinder 22.
But if grinding is done with the end face of the wheel pilot portion 9a as a reference, it is impossible to ensure run-out accuracy of the brake rotor mounting surface of relative to the bearing raceway 7 (that is, rotation center), and the coaxiality of the brake pilot portion 9b. 
Thus, heretofore, as measures for reducing run-out of the wheel-mounting flange 6 with the hub ring 2a alone, after grinding, secondary turning with the fitting surface 10a and abutment surface for the raceway member 2b as a reference was necessary.
An object of this invention is to provide a method and apparatus of working a hub ring in a wheel bearing assembly which can improve the runout accuracy of the flange surface to which a brake rotor is mounted and the coaxiality of the brake pilot portion to make secondary turning of the hub wheel unnecessary.
According to this invention, there is provided a method of working a hub ring of a wheel bearing assembly having integrally a wheel-mounting flange, a brake pilot portion protruding from the root of the wheel-mounting flange, and a small-diameter portion formed with a bearing raceway on outer periphery thereof, wherein with the brake pilot portion of the hub ring clamped, with a backing plate in abutment with an outer side face of the wheel-mounting flange, by axially biasing an end face of the small-diameter portion of the hub ring with a pressure clamp, at least the bearing raceway of the hub ring is ground with the outer side face of the wheel-mounting flange as a reference surface.
By grinding at least the bearing raceway of the hub ring with the outer side face of the wheel-mounting flange as a reference surface, it is possible to restrain the run-out of the wheel-mounting flange relative to the bearing raceway.
Also, because the hub ring is clamped by holding the brake pilot portion of the hub ring and axially biasing the end face of the small-diameter portion of the hub ring with the pressure clamp, the axis center accuracy of the hub ring is high and the coaxiality of the brake pilot portion improves.
The rotary grinding device for a hub ring according to this invention includes a clamp device for the hub ring comprising a chucking device for holding the brake pilot portion of the hub ring, a backing plate to be brought into abutment with an outer side face of the wheel-mounting flange, a pressure clamp for axially biasing an end face of the small-diameter portion of the hub ring, and a grinder used in abutment with at least the bearing raceway of the hub ring. With this device, since at least the bearing raceway is ground while ensuring the axis center accuracy of the hub ring with the outer side of the wheel-mounting flange as a reference surface, it is possible to restrain the run-out of the wheel-mounting flange relative to the bearing raceway and ensure the coaxiality of the brake pilot portion.
By supporting the outer peripheral portion of the wheel-mounting flange with the backing plate, rotary support of the hub ring stabilizes more, so that high-precision grinding is assured.
If the backing plate and the wheel-mounting flange are brought not into entire surface abutment but partial abutment by a single or a plurality of support portions, the contact area decreases, so that it is possible to grind the hub ring without being influenced by the working accuracy of the wheel-mounting flange in the preceding step.
Also, by providing air nozzles in the support portions of the backing plate to remove foreign matter adhering to the support portion of the backing plate or the clamp portion of the brake pilot portion by air blown from the air nozzles, it is possible to prevent poor fitting due to biting of foreign matter.
Also, by forming a closed space inside with the backing plate in abutment with the outer side of the wheel-mounting flange, blowing air from the air nozzles into the closed space, detecting the air pressure, and checking for the presence of foreign matter based on the air pressure, it is possible to confirm the fitting state of the hub ring on the working device. That is to say, if foreign matter bites between the wheel-mounting flange and the backing plate, or if the hub ring is fitted obliquely, a gap is formed between the wheel-mounting flange and the backing plate, so that air leaks through the gap and the air pressure drops. Thus, by monitoring the air pressure, it is possible to check for fitting trouble of the hub ring.
Also, by providing a clamp head which can pivot its head at the tip of the pressure clamp for axially biasing the end face of the small-diameter portion of the hub ring, it is possible to suitably maintain the biasing direction of the pressure clamp to the center of axis without being influenced by the working accuracy of the end face of the small-diameter portion of the hub ring.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: